(13-03-10) Adiposity is inversely related to insulin sensitivity in relatively lean Chinese adolescents: a population-based twin study1,2,3

Fengxiu Ouyang, Katherine Kaufer Christoffel, Wendy J Brickman, Donald Zimmerman, Binyan Wang, Houxun Xing, Shanchun Zhang, Lester M Arguelles, Guoying Wang, Rong Liu, Xiping Xu and Xiaobin Wang

1 From the Mary AnnJ Milburn Smith Child Health Research Program (FO KKC BW SZ LMA RLXW)the Division of Endocrinology (WJBDZ) Department of Pediatrics Northwestern University Feinberg School of MedicineChildren's Memorial HospitalChildren's Memorial Research Center Chicago IL; the Institute for Biomedicine Anhui Medical University Hefei China (HX);the Center for Population Genetics University of Illinois at Chicago School of Public Health Chicago IL (GWXX).
2 Supported in part by grant R01 HD049059 from the National Institute of Child Health and Human Development; grant R01 HL0864619 from the National Heart, Lung, and Blood Institute; and grant R01 AG032227 from the National Institute of Aging.
3 Address requests for reprints and correspondence to X Wang, the Mary Ann and J Milburn Smith Child Health Research Program, Children's Memorial Hospital and Children's Memorial Research Center Department of Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, IL. E-mail: [email protected] .
Background: Adolescence is a critical period for rising adiposity and falling insulin sensitivity (IS), but the independent relation between adiposity and IS remains understudied.
Objective: The objective was to examine which adiposity measures are most strongly associated with IS in nondiabetic adolescents, whether sex-difference exists, and to what degree genetic or environmental factors affect the adiposity-IS relation.
Design: The study included 1613 rural Chinese adolescents (888 males) aged 13?20 y from a population-based twin cohort. We used graphic plots and linear mixed models to examine the relation of anthropometric and dual-energy X-ray absorptiometry?based measures of adiposity with IS [QUantitative Insulin-sensitivity ChecK Index (QUICKI), fasting serum insulin (FSI), homeostasis model assessment of insulin resistance (HOMA-IR)] and structural equation models to estimate genetic/environmental influences on these associations.
Results: In graphic analyses, participants in the highest quintile (quintile 5) of waist circumference (WC) and percentage body fat (%BF) had the lowest QUICKI and the highest FSI and HOMA-IR values for all age-sex groups. In regression models adjusted for age, Tanner stage, zygosity, and physical activity, all adiposity measures showed inverse associations with IS in both sexes, but WC explained the largest fraction of variance in IS measures (10?14%). Of the phenotypic correlations between adiposity measures and IS (?0.28 to ?0.38), 74?85% were attributed to shared genetic factors and 15?26% to common unique environmental factors in both sexes.
Conclusions: In these relatively lean Chinese adolescents, WC and %BF (quintile 5) are the adiposity measures most consistently and strongly associated with decreased IS in both sexes. To a large degree, shared genetic factors contribute to this association.

Source: Am J Clin Nutr 91: 662-671, 2010

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